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Old 29th October 2008
dk_netsvil dk_netsvil is offline
Real Name: Devon
Fdisk Soldier
Join Date: May 2008
Location: New York
Posts: 75

Maybe a little more information would be useful:

I have 3 mailservers behind a firewall running iptables. Each mailserver has it's own private 10.254.0.x IP address and currently all outbound mail appears to come from the public IP of the firewall which I'll call This firewall also has the internal IP which is the default gateway for each mailserver. Each mailserver also has an interface on the public network, but their default gateway is the internal address of the firewall.

What I had wanted to do was use iptables to spoof the IP of each mailserver's public IP for outgoing mail. What I am slowly coming to understand is that this shouldn't be possible. I don't think iptables will allow you to spoof IPs that are already in use and not assigned to the current firewall.

Is the solution to assign 3 new public IPs to the firewall as aliases and then use iptables to spoof outbound mail from each server statically mapped to each of those newly assigned alias IPs?
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